In recent years, as digital broadcast environment is constructed and the demand for a high picture quality and a variety of supplementary services increases rapidly, digital broadcast service has been commercialized. Digital broadcast service can provide a high quality of service, which could not be provided in existing analog broadcast service.
In particular, Internet protocol television (IPTV) service that provides broadcast service over an IP network can not only provide a high picture quality of broadcast content, but enables bidirectional service, so it enables a user to actively select the type, audience time, etc. of a viewing program.
IPTV service can also provide a variety of supplementary services, for example, Internet search, home shopping, and on-line game in conjunction with broadcast based on this bidirectionality.
For this IPTV service, a service system and a user system may be required. The service system can be provided with various contents from a content provider, and it can generate guide information, including a service content list, a broadcast schedule, preview, etc., for example, electronic program guide (EPG), interactive program guide (IPG), content program guide (CPG), and so on and provide it to the user system over an IP network.
The user system is equipped with an IPTV device (for example, an IPTV set-top box), etc. The user system can display guide information provided from the service provider and request content or service, which is selected by a user, from the service system. Meanwhile, the user system can include a user domain. Content on the user side, which is received by the IPTV device, can be shared by devices within the user domain, for example, home network devices.
In order to stably operate this IPTV system, there is necessarily required a security system which can safely protect IPTV service related content, for example, multi-media content, DRM codes, software, message, etc. from illegal acts when downloading them onto a user system. The security system must be able to define a signature structure, a certificate structure, etc., which are used in authentication, and present an efficient signing process and authentication process so as to increase rapidness and security and therefore guarantee reliability of IPTV service. Accordingly, there is an urgent need for technical development of a corresponding field.